Manually-controlled arc flash energy reduction system and method for circuit breaker trip units

ABSTRACT

A circuit protection system includes a normal mode and a maintenance mode. A current sensor senses current in the circuit. An enclosure includes an access panel that is movable between a closed position and open position. A circuit breaker is mounted within the enclosure. An electronic trip unit is in communication with the current sensor and controls interruptions of the current by the circuit breaker based on a trip setting. An interface device is accessible when said access panel is closed and allows selections of the normal and maintenance modes. A display, which is in communication with both of the user interface device and the electronic trip unit, monitors the interface device and transmits data to the trip unit that is based on the selected mode. The display receives data from the trip unit and displays information based on the received data. The display is viewable when the access panel is closed. The trip unit changes the trip setting when said maintenance mode is selected to reduce potential arc flash energy.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/683,291, filed Mar. 7, 2007, which claims the benefit of U.S.Provisional Application No. 60/780,739, filed Mar. 9, 2006. Thedisclosure of both U.S. patent application Ser. No. 11/683,291, filedMar. 7, 2007, and U.S. Provisional Application No. 60/780,739, filedMar. 9, 2006, are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to electrical overcurrent protectiondevices, particularly electronic trip circuit breakers having amanually-controlled arc flash energy reduction system.

2. Description of Related Art

Overcurrent protection devices (OPDs) are used in electricaldistribution systems to protect electrical conductors and equipmentagainst the effects of short circuits, ground faults, and/or overloads(hereinafter “faults”). The OPDs in an electrical distribution systemare often selectively coordinated so that the nearest OPD upstream to afault will open and clear the fault before another further upstream OPDopens. Selective coordination of OPDs limits the number of distributioncircuits that are de-energized by the operation of an OPD in response toa fault. However, selective coordination of OPDs may also result inadded time delays that could allow more energy to be released during afault than would have been released had the OPDs not been selectivelycoordinated.

The OPDs in an electrical distribution system can be circuit breakershaving programmable electronic controllers for controlling the OPDs'trip settings. The programmable electronic trip controllers are known aselectronic trip units and circuit breakers employing electronic tripunits are known as electronic trip circuit breakers. Selectivecoordination among electronic trip circuit breakers is achieved byappropriately adjusting the trip settings of the electronic trip units.

Electronic trip circuit breakers may accommodate zone selectiveinterlocking (ZSI). In a ZSI system, a communication system existsbetween an upstream circuit breaker and all circuit breakers immediatelydownstream from the upstream breaker. A protection “zone” is formed thatextends to the line side of the downstream circuit breakers

The upstream circuit breaker uses a first set of settings (collectivelyreferred to as a “first trip setting”) that provide fast interruptionfor faults located in its protection zone (i.e., faults occurringbetween the upstream circuit breaker and a downstream circuit breaker).The upstream circuit breaker uses a second set of settings (collectivelyreferred to as a “second trip setting”) for faults located outside ofits protection zone (e.g., faults occurring downstream of a downstreamcircuit breaker). The second trip setting operates more slowly than thefirst trip setting and is coordinated with a trip setting for thedownstream circuit breaker. Because the first trip setting provides afaster interruption than the second trip setting, less energy may bereleased during a fault that occurs within the upstream circuitbreaker's protection zone than a fault occurring outside of the zone.

The second trip setting provides selective coordination with thedownstream circuit breakers and, therefore, has added time delays thatmay allow more energy to be released during a fault that occurs outsideof the upstream circuit breaker's protection zone. Selectivecoordination between upstream and downstream breakers is achieved byadding time delays to the electronic trip unit of the upstream breakerto thereby give the downstream breaker time to interrupt the fault.

In a ZSI system, when a downstream circuit breaker detects a fault, itwill send a restraint signal to the upstream circuit breaker. Theupstream circuit breaker, upon seeing the restraint signal, willrecognize that the fault is outside of its protection zone and begin totime out based on its second trip setting. In a first scenario, if thedownstream circuit breaker operates properly, it will trip and clear thefault before the upstream circuit breaker times out. Further, theupstream circuit breaker will determine that the fault has stopped andwill stop timing using its second trip setting and, thus, will not trip.In this first scenario, the downstream circuit breaker cleared the faultand minimal distribution lines were affected.

In a second scenario, if the downstream circuit breaker does not operateproperly, the second trip setting on the upstream circuit breaker willtime out and the upstream breaker will trip and clear the fault. Thus,the upstream circuit breaker acts as a back up circuit breaker to thedownstream circuit breaker. In this second scenario, however, alldistributions lines downstream from the tripped upstream circuit breakerare de-energized and additional fault energy was released.

In a third scenario, if the upstream circuit breaker detects a fault anddoes not receive a restraint signal from a downstream circuit breaker,the upstream breaker will recognize that the fault is within itsprotection zone and use its fast first trip setting, thereby minimizingthe energy released during the fault.

One drawback of a ZSI system is that control wiring and conduit must beinstalled between upstream and downstream circuit breakers, so thatrestraint signals can be monitored by the upstream circuit breaker.

A fault condition could cause an electrical arc that is harmful tonearby persons or property, due to the incident energy of the arc flash.It would be desirable to limit the duration of such an arc, and,therefore, the incident energy of the arc flash. It would further bedesirable to limit the incident energy of an arc flash while alsominimizing or eliminating the need to install wiring and conduit betweenOPDs as required for a ZSI system. One method of limiting the durationof an arc caused by a fault condition is by adjusting the trip settingsof an electronic trip circuit breaker to lower and/or faster settings.However, selective coordination may be lost by such an adjustment. Itwould be desirable to provide an electronic trip circuit breaker havinga convenient trip adjustment for temporarily adjusting trip settings tolower and/or faster settings.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect, provided is a circuit protection systemhaving a normal mode and a maintenance mode in which potential arc flashenergy is reduced. A current sensor senses electrical current in thecircuit. An enclosure includes an access panel that is movable between aclosed position and open position in which an interior of the enclosureis accessible. A circuit breaker for automatically interruptingelectrical current is mounted within the enclosure. An electronic tripunit is in communication with the current sensor and controls automaticinterruptions of the electrical current by the circuit breaker based ona trip setting. A user interface device, which is accessible when saidaccess panel is in the closed position, allows user selections of saidnormal mode and said maintenance mode. A display, which is incommunication with both of the user interface device and the electronictrip unit, monitors the interface device and transmits data to the tripunit that are based on the selected mode. The display receives data fromthe trip unit and displays information based on the received data. Thedisplay is viewable when said access panel is in the closed position.The electronic trip unit is adapted to change the trip setting when saidmaintenance mode is selected such that potential arc flash energy isreduced.

In accordance with another aspect, provided is a circuit protectionsystem having a normal mode and a maintenance mode in which potentialarc flash energy is reduced. A current sensor senses electrical currentin the circuit. An enclosure includes an access panel that is movablebetween a closed position, and an open position in which an interior ofthe enclosure is accessible. A circuit breaker is mounted within theenclosure. The circuit breaker automatically interrupts the electricalcurrent. An electronic trip unit is in communication with the currentsensor. The electronic trip unit controls automatic interruptions of theelectrical current by the circuit breaker based on a trip setting thatincludes a ground fault current pickup setting, a normally disabledmaintenance mode ground fault current pickup setting, a normallydisabled maintenance mode instantaneous current pickup setting, and atleast one of a short time current pickup setting and an instantaneouscurrent pickup setting. A display is mounted to the access panel and isviewable when the access panel is in the closed position. The displayreceives data from the trip unit and displays information based on thereceived data. A selector switch is mounted to the access panel and ismanipulable when the access panel is in the closed position. Theselector switch allows user selections of said normal mode and saidmaintenance mode. The electronic trip unit enables the maintenance modeinstantaneous current pickup setting and the maintenance mode groundfault current pickup setting when said maintenance mode is selected sothat potential arc flash energy is reduced.

In accordance with another aspect, provided is a method of modifying acircuit protection system. The method includes the steps of providing acurrent sensor for sensing electrical current in the circuit andproviding a circuit breaker for automatically interrupting theelectrical current. The circuit breaker is mounted within an enclosurehaving an access panel that is movable between a closed position and anopen position in which an interior of the enclosure is accessible. Thecircuit breaker includes an electronic trip unit in communication withthe current sensor. The method further includes the step of replacingthe electronic trip unit with another electronic trip unit having atleast the following settings: a long time current pickup setting, a longtime delay setting, a short time current pickup setting, a short timedelay setting, an instantaneous current pickup setting, a ground faultcurrent pickup setting, a ground fault delay setting, a maintenance modeinstantaneous current pickup setting that is normally disabled, and amaintenance mode ground fault current pickup setting that is normallydisabled. The method further includes the step of installing a displayso that the display is in communication with said another electronictrip unit and is accessible when said access panel is in the closedposition. The method further includes the steps of displayinginformation on the display based on data received from said anotherelectronic trip unit, and installing a selector switch for allowing userselections of a normal mode and a maintenance mode. The selector switchis installed so as to be accessible when said access panel is in theclosed position. The method further includes the step of enabling themaintenance mode instantaneous current pickup setting and themaintenance mode ground fault current setting whenever the maintenancemode is selected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a circuit breaker electronic trip unithaving a manually-controlled arc flash energy reduction system;

FIG. 2 is an exterior perspective view of an enclosure for a circuitbreaker having a manually-controlled arc flash energy reduction system;and

FIG. 3 is an interior perspective view of an enclosure for a circuitbreaker having a manually-controlled arc flash energy reduction system.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

An arc flash during a fault could harm nearby persons and/or property.Such harm could be mitigated by reducing the potential arc flash energyof the arc flash.

One equation for determining potential arc flash in a cubic box is:

E=1038.7×D ⁻¹⁴⁷³⁸ ×t×(0.0093×F ²−0.3453×F+5.9675)

where E is the energy level in cal/cm² in a box not larger than 20inches, D is the distance from an electrode in inches (for distances of18 inches and greater), t is the arc duration in seconds, and F isavailable fault current in kA (for the range of 15 to 50 kA). From theabove equation, it can be seen that at a given distance, potential arcflash energy can be reduced by shortening the duration of the arc.

FIG. 1 provides a schematic diagram of a circuit breaker electronic tripunit 1 having a manually-controlled arc flash energy reduction system.The electronic trip unit 1 is operatively connected to the operatingmechanism of a circuit breaker 2, for example, a three-pole circuitbreaker. The trip unit 1 is also operatively connected to a plurality ofcurrent sensors 3, for example, current transformers (CTs). Theelectronic trip unit 1 controls the circuit breaker's 2 operatingmechanism based on a plurality of settings (collectively referred to asa “trip setting”) and a current level in the circuit that is sensed bythe CTs. The trip unit 1 signals the circuit breaker's 2 operatingmechanism to open the circuit breaker whenever a fault condition occurs.

The electronic trip unit 1 includes, among other settings, the followingsettings: a long time current pickup setting, a long time delay setting,a short time current pickup setting, a short time delay setting, aninstantaneous current pickup setting, a ground fault current pickupsetting, a ground fault delay setting, a maintenance mode instantaneouscurrent pickup setting that is normally disabled, and a maintenance modeground fault current pickup setting that is normally disabled. Inputdevices on the trip unit 1 allow a user to program setpoint levels forthe various settings.

When the arc flash energy reduction system is disabled, the system is inthe “normal mode.” In normal mode, the instantaneous current pickupsetting and/or the ground fault current pickup setting may be enabled ordisabled as desired. For example, selective coordination with downstreamcircuit breakers may require that the instantaneous current pickupsetting be disabled. Further, in normal mode, the maintenance modeinstantaneous current pickup setting and the maintenance mode groundfault current pickup setting are disabled. That is, while in normalmode, the electronic trip unit 1 ignores the maintenance modeinstantaneous current pickup setting and the maintenance mode groundfault current pickup setting. When the arc flash energy reduction systemis enabled, the system is in the “maintenance mode.” In maintenancemode, the maintenance mode instantaneous current pickup setting and themaintenance mode ground fault current pickup setting are enabled, and,therefore, not ignored by the electronic trip unit. In an embodiment,when the maintenance mode instantaneous current pickup setting and themaintenance mode ground fault current pickup setting are enabled, theyoperate in addition to the instantaneous current pickup setting and theground fault current pickup setting, which remain enabled if enabled innormal mode. In another embodiment, when the maintenance modeinstantaneous current pickup setting and the maintenance mode groundfault current pickup setting are enabled, they operate as an alternativeto the instantaneous current pickup setting and the ground fault currentpickup setting, which are disabled in maintenance mode. In anembodiment, when the system is in the maintenance mode, at least one ofthe short time current pickup setting and the instantaneous currentpickup setting are disabled and the maintenance mode instantaneouscurrent pickup setting is enabled.

The maintenance mode instantaneous current pickup setting provides afaster tripping of the circuit breaker 2 than the short time currentpickup setting and can provide a faster tripping than the instantaneouscurrent pickup setting. Similarly, the maintenance mode ground faultcurrent pickup setting provides a faster tripping of the circuit breaker2 than the ground fault current pickup setting. Accordingly, when inmaintenance mode, the circuit breaker 2 can clear a fault more quicklythan in normal mode. In maintenance mode, the potential arc flash energydue to a fault is reduced, and maintenance can be performed more safelyon energized equipment downstream from the circuit breaker 2.

When in maintenance mode, the circuit breaker 1 behaves like a ZSIcircuit breaker that fails to receive a restraint signal and respondsquickly to a fault. By responding quickly to a fault, incident arc flashenergy is reduced. However, maintenance mode may not provide selectivecoordination of OPDs. In normal mode, selective coordination in theelectrical distribution system is preserved.

The electronic trip unit 1 is connected to a display 4. The connectionbetween the trip unit 1 and display 4 could be through a hardwired orwireless connection and provides a communications transmission pathbetween the trip unit 1 and display 4. FIG. 1 shows the electronic tripunit 1 and display 4 connected by a cable 5. The cable includes a plug 6at either end for plugging into communication port jacks on the tripunit 1 and display 4. The plugs 6 provide a readily removable connectionbetween the trip unit 1 and display 4.

The display 4 communicates with the trip unit 1. The display 4 receivesdata from the trip unit and displays messages based on the data. Forexample, the display 4 could display various circuit breaker settings,present current level in the circuit, historical trip data, and thelike.

The display 4 can include a battery system for powering the display 4.Alternatively, the display 4 can be powered through its interconnectionwith the trip unit 1. For example, both of the trip unit 1 and thedisplay 4 can be powered by the CTs 3. The display 2 can also be poweredfrom a power source local to the display 4.

A user interface device, such as a selector switch 7, is connected tothe display 4. The display 4 monitors the position or state of theselector switch 7 and communicates the state of the selector switch 7 tothe trip unit 1. The selector switch 7 would typically be mounted nearthe display 4. Because the selector switch 7 is connected directly tothe display 4, and not the trip unit 1, a single cable 5, such as aribbon cable, can be run between the trip unit 1 and display/selectorswitch location. Furthermore, the cable 5 can be readily disconnectedfrom the trip unit 1 by removal of either plug 6, which facilitatesremoval of the circuit breaker 2 and/or the trip unit 1 for maintenance,replacement, etc.

The selector switch 7 can be a two-position selector switch having an ONposition and an OFF position, for manually enabling and disabling thearc flash energy reduction system. The selector switch 7 can be lockedin the ON or OFF position. For example, the selector switch 7 caninclude an operating handle or switch cover that accommodates a padlock,or the selector switch can have an integral key locking mechanism. Theselector switch 7 can also be compatible with standard lockout/tagoutdevices. In an embodiment, the selector switch 7 includes a plurality ofnormally closed and/or normally open auxiliary contacts for monitoringby and/or interlocking with various other devices. The selector switch 7can alternatively be formed from a variety of known switches, such as apushbutton switch, a membrane switch, or a touchscreen interface device,for example.

The display 4 includes an electronic controller, for example, amicroprocessor or microcontroller, and is configured to communicate withthe trip unit 1, which also includes an electronic controller. Thedisplay 4 further includes indicating lights, for example, LEDindicating lights 8, and an alphanumeric/graphical display system, forexample, a liquid crystal display (LCD) 9. Through the indicating lightsand the alphanumeric/graphical display system, the display 4 can provideinformation to a user regarding various circuit breaker settings,present current level in the circuit, historical trip data, informationabout the display 4 itself, and/or the position of the selector switch7. For example, indicating lights can be provided to indicate that thedisplay 4 is working properly, the existence of an overcurrentcondition, or that the selector switch 7 is in the ON or OFF position.

The display 4 can be configured to display the following information onthe LCD 9: CT rating, long time current pickup setting, long time delaysetting, short time current pickup setting, short time delay setting,short time I²T, instantaneous current pickup setting, ground faultcurrent pickup setting, ground fault delay setting, ground fault I²T,phase unbalance current pickup setting, phase unbalance delay setting,maintenance mode ground fault current pickup setting, maintenance modeinstantaneous pickup setting, last trip data, ground fault >2 times CTrating, phase unbalance percentage, historical trip data, low currentcondition, overload condition, phase A, B, and C currents, ground faultcurrent, and line-to-line and line-to-neutral voltages. A button 10 isprovided on the display 4 for selecting the information to be displayedon the LCD 9. For example, a user can sequentially toggle among theinformation that can be displayed on the LCD 9 by repeatedly pressingthe button 10. The display's 4 electronic controller monitors the button10 and causes information to be displayed on the LCD 9 in response touser selections. In an embodiment, various settings of the trip unit 1,for example the trip setting, can be set at the display 4 and not merelydisplayed at the display 4. In a further embodiment, the varioussettings of the trip unit 1 cannot be changed at the display 4, toprevent unauthorized changes.

The display 4 can communicate the position or state of the selectorswitch 7 to the trip unit 1. A user places the circuit protection systemin maintenance mode by moving the selector switch 7 to the ON position.When the selector switch 7 is moved to the ON position, the display 4sends data to the trip unit 1 to inform the trip unit of the position ofthe selector switch. In an embodiment, the trip unit 1 responds to themovement of the selector switch 7 to the ON position by enabling themaintenance mode instantaneous current pickup setting and themaintenance mode ground fault current pickup setting for as long as theselector switch 7 is in the ON position. In a further embodiment, thetrip unit 1 responds by also disabling the ground fault current pickupsetting and disabling at least one of the short time current pickupsetting and the instantaneous current pickup setting. In a still furtherembodiment, the trip unit 1 responds by adjusting the instantaneouscurrent pickup setting and the ground fault current pickup setting basedon, for example, the maintenance mode instantaneous current pickupsetting and the maintenance mode ground fault current pickup setting.For example, in the maintenance mode, the instantaneous current pickupsetting can be replaced with the maintenance mode current pickup settingand the ground fault current pickup setting can be replaced with themaintenance mode ground fault current pickup setting. In a still furtherembodiment, the trip unit responds to the movement of the selectorswitch 7 to the ON position by adjusting the ground fault delay settingto a lower setting, such as a minimal delay setting.

A maintenance technician can place the circuit protection system inmaintenance mode by placing the selector switch 7 in the ON position. Ifdesired, the maintenance technician can lock the circuit protectionsystem in maintenance mode by placing a padlock onto the switch'soperating handle or lockable cover.

In an embodiment, the maintenance mode ground fault current pickupsetting ranges from of 20% to 200% of the CT rating, with a maximum of1200 amps, and is adjustable in 10 amp steps. However, other rangesand/or settings are also possible. In an embodiment, the maintenancemode ground fault current pickup setting can be turned off or disabled,so that the electronic trip unit 1 uses no maintenance mode ground faultpickup setting when the selector switch 7 is in the ON position. In anembodiment, the maintenance mode instantaneous pickup setting rangesfrom 150% to 1200% of the long time current pickup setting, and isadjustable in 100 amp steps. However, other ranges and/or settings arealso possible. By appropriately selecting and setting the maintenancemode ground fault current pickup setting and maintenance modeinstantaneous pickup setting, arc flash potential downstream of thecircuit breaker 2 can be reduced, due to a reduced breaker clearingtime.

FIGS. 2 and 3 show an example mounting configuration for the display 4and selector switch 7. The display 4 and selector switch 7 are mountedto a circuit breaker enclosure 11. More specifically, they are mountedto an access panel, such as a door 12, for the circuit breaker enclosure11. In FIG. 2, the door 12 is closed, and the display 4 and selectorswitch 7 are accessible while the door 12 is closed. A maintenancetechnician can operate the selector switch 7 and view information aboutthe circuit breaker on the display 4 without opening the door 12 andpossibly exposing himself to electrically energized parts. In FIG. 3,the door 12 is open and the trip unit 1 is accessible. As discussedabove, a single cable 5 connects the trip unit 1 and the display 4.

An existing electrical distribution system can be modified to provide amanually-controlled arc flash energy reduction system as discussedabove. For example, an installation may have existing electronic tripcircuit breakers in enclosures. However, the existing electronic tripunits may not include the maintenance mode instantaneous current pickupsetting and the maintenance mode ground fault current pickup setting.These existing electronic trip units can be removed and replaced withelectronic trip units having such settings. Mounting holes for thedisplay and selector switch can be drilled or punched out of the accesspanel of the circuit breaker enclosure. The display and selector switchcan then be mounted to the access panel, the selector switch wired tothe display, and a cable run between the display and new electronic tripunit.

In an embodiment, the trip unit 1 does not include the maintenance modeground fault current pickup setting and the maintenance modeinstantaneous current pickup setting, and the display 4 and/or trip unit1 automatically adjusts the ground fault current pickup setting and theinstantaneous current pickup setting whenever the selector switch 7 ismoved to the ON position.

In an embodiment, normal mode and maintenance mode settings are storedin a memory portion of the display 4. As the selector switch 7 is movedbetween the ON and OFF positions, the display 4 communicates theappropriate settings to the trip unit 1, overwriting a prior settingsstored within the trip unit 1. In this embodiment, the display 4 acts asa remote programmer for the trip unit 1. In an embodiment, the display 4downloads and saves the trip unit's 1 normal mode settings in responseto the selector switch 7 being moved to the ON position. The display 4then communicates the position of the selector switch 7 to the trip unit1 and/or overwrites the trip unit's 1 normal mode settings withmaintenance mode settings. When the selector switch is moved to the OFFposition, the display 2 communicates this to the trip unit 1 and/oroverwrites the maintenance mode settings with the previously downloadedand saved normal mode settings.

In an embodiment, the electronic trip unit 1 and the display 4 cancommunicate with other devices, such as a programmable controller, forexample, a programmable logic controller, a remote terminal unit, or ahuman-machine interface device.

It should be evident that this disclosure is by way of example and thatvarious changes may be made by adding, modifying or eliminating detailswithout departing from the fair scope of the teaching contained in thisdisclosure. The invention is therefore not limited to particular detailsof this disclosure except to the extent that the following claims arenecessarily so limited.

1. A circuit protection system, having a normal mode, and a maintenancemode in which potential arc flash energy is reduced, comprising: acurrent sensor for sensing electrical current in the circuit; anenclosure having an access panel that is movable between a closedposition and open position in which an interior of the enclosure isaccessible; a circuit breaker, mounted within the enclosure, forautomatically interrupting the electrical current; an electronic tripunit in communication with the current sensor for controlling automaticinterruptions of the electrical current by the circuit breaker based ona trip setting; a user interface device, which is accessible when saidaccess panel is in the closed position, that allows user selections ofsaid normal mode and said maintenance mode; and wherein when themaintenance mode is selected using the user interface device, theelectronic trip unit changes the trip setting such that potential arcflash energy is reduced, and wherein when said maintenance mode isselected, the electronic trip unit changes the trip setting by enablingboth of a maintenance mode instantaneous current pickup setting and amaintenance mode ground fault current pickup setting.
 2. The circuitprotection system of claim 1, wherein the access panel is a door.
 3. Thecircuit protection system of claim 1, wherein the user interface is aselector switch that is accessible when said access panel is in theclosed position and having means for receiving a padlock without openingthe access panel.
 4. The circuit protection system of claim 1, whereinthe electronic trip unit includes: a long time current pickup setting; along time delay setting; a short time current pickup setting; a shorttime delay setting; an instantaneous current pickup setting; a groundfault current pickup setting; a ground fault delay setting; wherein themaintenance mode instantaneous current pickup setting is normallydisabled; and wherein the maintenance mode ground fault current pickupsetting is normally disabled.
 5. The circuit protection system of claim4, wherein when said maintenance mode is selected, the electronic tripunit disables the ground fault current pickup setting and at least oneof the short time current pickup setting and the instantaneous currentpickup setting.
 6. A circuit protection system, having a normal mode,and a maintenance mode in which potential arc flash energy is reduced,comprising: a current sensor for sensing electrical current in thecircuit; an enclosure having an access panel that is movable between aclosed position and open position in which an interior of the enclosureis accessible; a circuit breaker, mounted within the enclosure, forautomatically interrupting the electrical current; an electronic tripunit in communication with the current sensor for controlling automaticinterruptions of the electrical current by the circuit breaker based ona trip setting; and a user interface device, which is accessible whensaid access panel is in the closed position, that allows user selectionsof said normal mode and said maintenance mode; wherein when saidmaintenance mode is selected using the user interface device, theelectronic trip unit changes the trip setting such that potential arcflash energy is reduced, wherein the electronic trip unit includes: aninstantaneous current pickup setting; a ground fault current pickupsetting; a maintenance mode instantaneous current pickup setting; and amaintenance mode ground fault current pickup setting, wherein when saidmaintenance mode is selected, the electronic trip unit changes the tripsetting by replacing the instantaneous current pickup setting with themaintenance mode instantaneous current pickup setting and replacing theground fault current pickup setting with the maintenance mode groundfault current pickup setting.
 7. The circuit protection system of claim6, wherein the access panel is a door.
 8. The circuit protection systemof claim 6, wherein the user interface is a selector switch that isaccessible when said access panel is in the closed position and havingmeans for receiving a padlock without opening the access panel.